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Improve Hummer H1 HVAC System - Automotive

Greetings from Florida,

I am new to these forums and I am here to learn how best to improve the Automotive HVAC system in my Hummer H1. I am learning and I am not afraid to do research and become educated, but I have very little experience with HVAC in general.

H1's produced up until 1997.5 had an electro servo motor flap operating system. In 1998, a newer system was installed that was vacuum controlled.
The early system performs very poorly in hot climates. It is very common for pre-1997.5 H1's to be upgraded to the 1998-2004 cooling system, at a cost of $3,000 USD and 3 days worth of labour. This involves substantial cost and down time for the vehicle and a lot of cutting and modifying of vehicle components to alter the electro servo motor system to the vacuum system.

I have a limited edition truck and I want colder A/C, but I do not want to deal with "hacking up" a limited edition truck to install the upgraded HVAC system.

So far, I have done the following:

1. Bypassed heater core (No more heater or hot water mixing)
2. Charged system fully (R134A) and added Ice32
3. Added extra cold air ducts and hoodscoop in front of vehicle to increase air flow (Factory OEM upgrades)
4. Had truck taken to several different Automotive HVAC technicians that I did due-diligence on, that are experienced.

I noticed that the HVAC temperature was always "comfortable" when it was raining outside, or when I was driving durning evening hours with no sun...but during the heat of the day, it does not cool worth a darn.

One of the techs looked at the condenser and poured water over the condenser while reading the R134A gauges. There was a significant drop in temperature on the R134A gauges. He has recommended a new condenser with parallel flow coils and adding a cooling fan on top of the condenser, because a fan is not installed on H1's condensers from the factory, but an aftermarket SPAL unit is available.

I also looked at the dryer and noted that on the later Hummer H1's, the increased the size of the filter/dryer assembly. I did some research and found a filter/dryer that will fit in the stock mounting location, that will give me double the internal volume compared to the factory OEM filter/dryer. I have read that increasing the internal volume of the filter/dryer will give the freon more room to expand, therefore, making the air cooler.

A friend of mine is a retired Airconditioning man of 40 years experience and former automobile technician. On his Ford Retractable with Factory A/C, he retrofitted the aftermarket system from R134A to R12. He is a die-hard R12 fan and says that the vent temperatures were 8-10 degrees cooler with R12 versus the R134A. He offered to convert my H1 in an EPA certified facility.

So here are the questions:

1. Based on the test of pouring water over condenser and seeing significant drops in temperatures, a new, high efficiency condenser should help, along with a "pusher" fan mounted on top, correct?
2. By using a larger filter/dryer with double the internal volume of the factory filter/dryer, do you expect that this will help with achieving lower A/C temps?
3. Cost no object on refrigerant- Should I flush the system for 10 hours and attempt a R134A to R12 conversion??? I know I need to remove the compressor and drain the oil and make sure that the system has been flushed very well due to oil compatability. I looked at the new parallel flow condenser and the filter/dryer and *both* are rated for R12 and R134A.
4. Can I get cooler temperatures with George Goble's refrigerants- ie. CoolTop/Autofrost/R406?

Thanks for your time. I am learning here. I would love to have ice cold A/C!

The size of the dryer will not be a help to you. Although I have never seen a Hummer in the shop (when I was a master tech) I recall that GM favors a cycling clutch orifice tube metering system what has an accumulator, and not a liquid dryer. The only functions of that device are to expose some 134A dessicant to the refrigerant to remove any moisture and more important, to allow any liquid from the evap to boil off so only vapor enters the compressor. You don't need a larger accumulator, and if for some reason GM decided to go with a TXV system, then you would not need a larger dryer, either..

The tech who cooled the condenser with water is on the right track.

If you have room for it, having the tech install a larger condenser with dual electric fans would be the approach I would take. When I did conversions from 12 to 134A I nearly always had to add a fan. Your standard viscous clutch engine fan cannot move enough air over that condenser to remove the heat, and heat removal is the name of the game.

I would not go back to 12.

To test the effectiveness of additional condenser cooling, idle the truck in your driveway on a hot day and have someone spray water from a hose on the condenser while you evaluate the effectiveness from inside the truck. If you are happy with the result, have your AC tech upgrade the condenser, give it two fans (one side of the condenser is good enough) or do both of those things.

And please have a tech do ALL the work. I don't want you getting injured.

2. The vehicle came from the factory with R134A. I noticed that the receiver/dryer, condenser and compressor are all rated for use with either R134A -OR- R12. So my question is, what if I converted my R134A system to R12??? I understand R12 leaks less and it cools much better.

3. Autofrost, Cooltop, R406, etc...I understand that there are "aftermarket" improved freon choices. Would there be a benefit to me if I used one of these over "off the shelf" R12 or R134A?

4. I will perform the driveway hose test. Like I said, whenever it rains while I am driving the truck, I am comfortable with the A/C performance inside. And at night, it performs well, also. So I guess this has more to do with a drop in the ambient air temperature, correct?

I wouls stick with 134A. Your pressure switches are designed to work with the specific pressures that are characteristic of that refrigerant. Your problem is a high ambient problem. That's why the system works better with less heat load on the vehicle. Try the fans first.

1. So a high ambient problem means high ambient temperature problem, correct? ie- A/C not cooling in 90 degree+ weather??

2. Is there any way to over-clock the blower motor, so that the CFM increases? I realize that the blower motor is controlled by the control head and the blower motor resistor pack. Just a thought....The volume of air is a little lacking, but if it blew colder, that would be the biggest boost in cabin comfort.

3. Fuji- are you referring to the fuel economy? It does better than an H2, weighs more and has a bigger engine with forced induction!

Thanks again gents.

Any other ideas you have to get better performance out of this system, please let me know. I am willing to try anything and am willing to spend money.

1. So a high ambient problem means high ambient temperature problem, correct? ie- A/C not cooling in 90 degree+ weather??

2. Is there any way to over-clock the blower motor, so that the CFM increases? I realize that the blower motor is controlled by the control head and the blower motor resistor pack. Just a thought....The volume of air is a little lacking, but if it blew colder, that would be the biggest boost in cabin comfort.

3. Fuji- are you referring to the fuel economy? It does better than an H2, weighs more and has a bigger engine with forced induction!

Thanks again gents.

Any other ideas you have to get better performance out of this system, please let me know. I am willing to try anything and am willing to spend money.

You already know the one (and hopefully, only) thing you should do. I would not advise you to be any more creative than that. Your components may say they are good for 134A or R12, but do not let that be a temptation for you in this system. It isn't designed for R12, it's just that the components MAY be used for either, and that does not apply to all components. Your accumulator contains a 134A dessicant, which is different from the desiccant used in an R12 system.

If anything, you might consider getting the entire vacuum system out of a yard vehicle, and having the tech change out the entire heater and AC box that is mounted to the firewall. That way, you have a system that exists in an identifiable model year, and greater satisfaction overall.

Add the fan, and let us know how it works out. The fan should be controlled by an accessory relay that is energized by the compressor control circuit. Your tech will have access to AllData and can easily decide where to tap in.